1. Field of the Invention
The present invention relates to a throttle valve position detecting system adapted for detecting that a throttle valve provided in the intake pipe of an automotive engine has reached a predetermined position.
2. Description of the Prior Art
A typical conventional throttle valve position detecting system is disclosed in Japanese Pre-Examination Patent Publication No. 53-13169 and has a rotary detector (referred to as "rotor" hereinunder) adapted for rotation with a throttle shaft carrying the throttle valve. The rotor has a guide groove which extends substantially in the direction of rotation of the rotor. The guide groove has a stepped configuration constituting a cam contour such that a movable contact received in this guide groove is displaced radially outwardly and inwardly when the rotor rotates in one and the other directions. A pair of stationary contacts, namely, a first stationary contact for detecting that the throttle valve has reached the fully open position and a second stationary contact for detecting that the throttle valve has reached the fully closed position, are disposed in alignment with the movable contact in the radial direction of the rotor. The movable contact and the two stationary contacts are assembled together to form a unit which will be referred to as "throttle switch" hereinunder.
In operation, when the rotor rotates as a result of the throttle valve operation, the movable contact is moved in the radial direction by the cam action of the guide groove into contact with one of the stationary contacts thus detecting that the throttle valve has reached the fully opened position or the fully closed position.
This known throttle valve position detecting system, however, requires a large space for accommodating all of three contacts; namely, one movable contact and two stationary contacts. In addition, for connecting these three contacts of the throttle switch to an electronic control unit (referred to as "ECU" hereinunder), the connector on the throttle switch is required to have three terminals. In consequence, the cost and the size of the throttle switch are increased undesirably. Furthermore, three electric lines have to be used to connect the throttle switch to the ECU, resulting in complicated construction of the throttle valve position detecting system.